1. Field of the Invention
This invention pertains to ring seals and more particularly to improvements in ring seals having a U-shaped recess cup opening in at least one side usually accommodating a similarly shaped spring.
2. Description of the Prior Art
Ring seals are employed in a wide range of designs for applications with rods, pistons and the like and in numerous additional custom configurations for use in static, reciprocating and rotary applications. A popular ring seal for premium applications is known as a spring energized polymeric ring seal. Generally, such a seal comprises a main body member made of a suitable polymeric material, such as a PTFE blend, configured so as to have a U-shape or channel recess that opens on one or both sides. The seal is "energized" by one or more suitable spring elements accommodated and conforming to the configuration of the recess. A usual material for such spring elements is stainless steel. Preferably, the spring is formed in a U-shape to provide cantilever beam action to the seal.
A ring seal is usually located within a suitable gland, usually metal, that limits its radial expansion. It may be pressured against such a gland or other axial limiting surface when in use. Seals of the type described have been employed in temperatures ranging from -475.degree. F. to +700.degree. F. and in pressure conditions up to 30,000 psi. Such seals are used in liquid and gas conditions and are often used where the conditions are also environmentally corrosive.
Although the ring seals just described are very useful, use in pressurized/depressurized and other types of variable conditions have caused the materials to prematurely age. Aging is caused by creep and seal extension. Further, in the high end of the pressure range, roughly between 14,000 and 30,000 psi, the high pressures tend to crush the lips of the openings.
Attempts to prevent such premature failures have included the use of stacking or the use of a back up ring to protect the open side of the U-shape cup recess opening. Stacking obviously does not protect the first ring seal, since it will be open to the pressure. When aligned face-to-face, the lips of the openings crush against each other. Even a back-up ring pushed back into the lips of a U-shape cup recess opening can cause crushing of the lips of the opening.
It should be mentioned that the "heel" of the body of the ring, i.e., the side of the ring opposite the open side, is generally a thick wall portion with a flat side normal to the axis of the ring and is provided to operate in the existing high pressure conditions and to stabilize the ring in the gland. Because of the structure of the heel, it is not possible to stack adjacent ring seals, in the same manner as with V-shaped seals where the thickness of the seals are of uniform dimension.
Therefore, it is a feature of the present invention to provide a ring seal structure including a suitable hat ring having a solid projection on one side for conforming with the U-shape cup or channel recess of the main body member of the seal.
It is another feature of the present invention to provide a ring seal assembly including the stacking of at least two sets of ring seal main body and hat ring combinations.
It is still another feature of the present invention to provide a stack assembly including a plurality of ring seals, i.e., main body and hat ring combinations, that can be stacked heel-to-heel, hat-ring-to-hat-ring, or heel-to-hat-ring.
It is yet another feature of the present invention to provide a stack assembly including combinations of ring seal main body rings, hat rings and back-up rings.